Why is being concerned with the marketability of a piece seen as a terrible thing?
Writing is a form of communication. Communication requires a sender and a receiver. Without concern for the reader/receiver, one might as well be writing in a private journal.
I can understand therapeutic writing. I do my share of it, but I don't feel entitled to have it published, just because I needed to write it. It is separate from the writing that I publish and want to publish.
Not every writer has the goal of traditional publication, I realize that. I have no objection to anyone saying, "These are my standards, I will write according to them." What I am irked by is when anyone says, "These are my standards and you are a horrible person if you don't write by them."
Your mileage, as usual, may vary.
Separate names with a comma.